First report of Epicoccum nigrum associated with leaf spot disease of cowpea ( Vigna unguiculata ) from India
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First report of Epicoccum nigrum associated with leaf spot disease of cowpea (Vigna unguiculata) from India Yelandur Somaraju Deepika 1,2 & Shivannegowda Mahadevakumar 3 & Kestur Nagaraj Amruthesh 3 & Nanjaiah Lakshmidevi 2 Received: 7 August 2020 / Accepted: 20 November 2020 # Società Italiana di Patologia Vegetale (S.I.Pa.V.) 2020
Keywords New disease record . Epicoccum nigrum . Molecular identification . Vigna unguiculata
Cowpea [Vigna unguiculata (L.) Walp.] is one of the important pulse crops cultivated in the arid and semiarid regions of the world. During the survey (2017-19) of diseases of crop plants in the month of June and July, a characteristic leaf spot disease was observed in the southern Karnataka region. The incidence ranged from 10–14% in around 80 ha of cowpea fields evaluated and surveyed. The initial symptoms recorded were small necrotic lesions on the adaxial leaf surface and gradually enlarged (up to 1.5 cm) causing severe defoliation and reduced plant vigor. On the abaxial surface, abundant conidia in the form of black sori were observed. Associated fungal pathogen was isolated on PDA medium and incubated at 28 ± 2 °C, 12 h alternate light and dark period. The fungal colony with aerial mycelia interspersed with dark cushion-shaped sporodochia consists of short, compact conidiophores bearing large isodiametric, solitary, muricate, brown, globular/ pear shaped conidia (26.21 ± 3.14–20.74 ± 2.46 µm). Further, ITS-rDNA and LSU region amplified using ITS1/ITS4 and LROR/LR7 primers and nucleotide sequences were deposited in GenBank with accession num-
Y. S. Deepika and S. Mahadevakumar contributed equally to this work. * Nanjaiah Lakshmidevi [email protected] 1
Department of Studies in Botany, University of Mysore, Manasagangotri, Mysore 570006, Karnataka, India
2
Department of Studies in Microbiology, University of Mysore, Manasagangotri, Mysore 570006, Karnataka, India
3
Applied Phytopathology Laboratory, Department of Studies in Botany, University of Mysore, Manasagangotri, Mysore 570006, Karnataka, India
bers MT816396-ITS and MW093067-LSU. BLASTn search of ITS and LSU sequence revealed 100% homology to Epicoccum nigrum Link, and E. layuense. However, phylogenetic analysis using the concatenated ITS and LSU sequences revealed that the fungus shared a common clade with reference sequence of E. nigrum and not with E. layuense. Thus the identity was confirmed as Epicoccum nigrum based on morphological and molecular sequence analysis (Mahadevakumar et al. 2014). Pathogenicity test was conducted on 45-day-old healthy cowpea plants by foliar application of conidial suspension (105 conidia/ml) along with controls. The appearance of leaf spot symptoms was observed 20 days post-inoculation. The pathogen was re-isolated and its identity was confirmed. Though E. nigrum has been reported as an endophyte in several medicinal plants (Fávaro et al. 2012). It is reported to cause disease on Lablab purpureus from India (Mahadevakumar et al. 2014), and post-harvest decay of cantalo
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